Multimode fiber (MMF) is the primary optical transmission medium in data centers, and it has enjoyed increased use as the number and size of data centers have expanded. Multimode fibers are classified under certain ISO standards based on the effective modal bandwidth (EMB), which is measured in “frequency×distance” units, e.g., MHz·km. The classifications are referred to using the acronym OM (for “optical multi-mode”), with the present OM standards being OM1, OM2, OM3 and OM4. Each OM-standard fiber has different physical characteristics (e.g., core radius, cladding radius, relative refractive index profile, etc.) that result in different performance characteristics, including different EMBs.
The various design parameters that define an OM-standard fiber are not perfectly reproduced in the manufacturing process. This results in substantial variation in the performance of a given OM-standard fiber, and in particular substantial in the EMB. As a consequence, fiber manufacturers measure select properties of their manufactured OM-standard fibers, such as EMB and OFL-BW. These measurements can also be used to pick the most suitable fibers for a given application for the measured properties at the measurement wavelengths. However, it is more difficult to select the most suitable fibers for use at wavelengths different from the one at which the measurements were made since it is not clear whether a given fiber in a group of supposedly like fibers can actually meet bandwidth requirements at two different wavelengths, such as at 850 nm and at 950 nm.